Hurricane Katrina sweeps across the States

Shopkeepers have sandbagged stores in the French Quarter of the vulnerable Gulf Coast city of New Orleans and workers boarded up city hall as a strengthening Hurricane Katrina churned across Gulf waters.

Officials in the low-lying city - famed for its Mardi Gras parades - urged residents to evacuate and stranded tourists to shelter on at least the third floor of their hotels as Katrina threatened to make a second and possibly more deadly assault on the US coast after killing seven people in Florida.

"I think there is a very good possibility it will indeed get stronger," Max Mayfield, director of the US National Hurricane Center, told WSVN television in Miami.

"This hurricane has the potential to cause extreme damage and large loss of lives if they don't take action very soon."

Computer models showed that New Orleans, much of which lies below sea level, could be in the storm's bull's eye.

They also indicated Katrina could grow into at least a Category 4 hurricane on the five-step Saffir-Simpson scale, with some strengthening forecast in the next 24 hours.

Some predictions saw it becoming a catastrophic Category 5 - like Hurricane Andrew which struck south of Miami in 1992 and ranks as the costliest natural disaster in U.S. history, or Hurricane Camille in 1969, which just missed New Orleans but devastated Louisiana and Alabama and killed more than 400.

New Orleans officials turned some major routes out of the city into one-way streets, helping to speed the exodus.

Mayor Ray Nagin said the Louisiana Superdome would become a giant shelter for people with special needs on Sunday. As for others, Nagin said he hoped "people are taking the necessary steps to leave the city of New Orleans."